Conventionally, an oxygen sensor has been disposed in an exhaust passage (exhaust pipe) of an internal combustion engine of an automobile or the like so as to detect the oxygen concentration of exhaust gas, on the basis of which the air-fuel ratio is controlled. An example of such an oxygen sensor is one which includes a gas detection element having at least one cell in which a pair of electrodes are formed on oxygen-ion conductive zirconia. However, there has been a problem in that accuracy in detecting oxygen concentration varies among individual oxygen sensors because of variation in output characteristic among the individual oxygen sensors and deterioration of each oxygen sensor with time.
In order to overcome the conventional problem, there has been proposed a technique of carrying out atmosphere correction in order to calibrate the relation between oxygen concentration and the output value of an oxygen sensor when the supply of fuel to an internal combustion engine is stopped and the interior of an exhaust passage is estimated to be in substantially the same condition as the atmosphere (for example, see Patent Document 1).
[Patent Document 1] Japanese Patent Application Laid-Open (kokai) No. 2007-32466 (paragraph 0040)